Project 1: Dystrophin delivery to muscle via myogenic progenitors (Chamberlain, JS, P.I.)- Skeletal muscles in Duchenne muscular dystrophy (DMD) patients undergo cycles of necrosis and regeneration leading to loss of muscle fibers and replacement with adipose and connective tissue. Regeneration is supported by activation and recruitment of satellite cells, but the regenerative capacity of dystrophic muscles decreases over time due to poorly understood changes in the muscle microenvironment perhaps coupled with the onset of proliferative senescence. Loss of regenerative capacity is a major contributingfactor to decreasing muscle strength, and leads to profound muscle wasting. One approach to treating DMD and other muscle wasting disorders is to identify and/or generate myogenic progenitor/stem cells either from donors or patients, expand them in vitro or in vivo and use these cells to at least partially restore muscle mass and regenerative capacity. However, satellite cell based therapies have so far failed and there is a great need for alternative stem cells with better potential to support muscle regeneration following transplantation. The goals of this project are to isolate and generate alternative stem cells from dystrophic muscles, to correct the genetic lesion in these cells by gene transfer, and to explore autologous transplantation into dystrophic mice. Towards these goals we have developed a robust system for generating lentiviral (LV) vectors that are able to permanently transduce a variety of dividing and non-dividing cells, including myoblasts, satellite cells, fibroblasts, pericytes and mesoangioblasts. LV (and AAV) vectors can also be directly injected into muscles (or blood vessels in the case of AAV) of mice, leading to gene expression in satellite cells and myofibers for the lifespan of a mouse. We have shown that fibroblasts from dystrophic mice can be genetically corrected and modified to form myogenic progenitors after transplantation into mdx hosts. We have also been exploring the isolation and genetic modification of pericytes for autologous cell therapy of muscular dystrophy. We propose to use fibroblasts directly and indirectly via induction of pluripotent stem (iPS) cells, and to compare their efficacy with that of pericytes upon transplantation into mouse models of DMD. RELEVANCE (See instructions): Our goal is to develop methods that could be used to treat the muscular dystrophies (MDs). Stem cell therapy is a promising approach, but many limitations prevent its implementation at present. Our studies are designed to identify an accessible source of muscle stem cells that could be used for autologous stem cell therapies, and to genetically manipulate those cells to produce the protein missing in common MDs.